The present invention relates to a magnetic valve.
More particularly, it relates to a magnetic valve which has an actuating element displaceable in a valve chamber between two end positions for a valve member for closing and releasing at least one valve opening, a permanent magnet arranged in the actuating element for holding the actuating element in the end positions, pole members arranged at both end sides of the actuating member, a transverse yoke, and an operating winding.
Magnetic valves of the above mentioned general type are known in the art. One of such magnetic valves is disclosed for example in the German document DE 4,000,071 Al. A known so-called bistable magnetic valve disclosed in this reference has an actuating element and a valve member combined to a valve piston. It is composed of a centrally arranged disc-shaped permanent magnet, two soft iron rings abutting against each disc surface of the permanent magnet and having central openings filled with elastomeric filling pieces and a sleeve shaped guiding cage which surrounds the permanent magnet and both soft iron rings undisplaceably. The end stops are formed as ferromagnetic closure pieces arranged coaxially on both sides of the valve piston at a distance from it and having central closure openings with mouths forming valve openings in the valve chamber. The end sides of the closure pieces which face the valve piston are formed as valve seats which cooperate with the elastomeric filling pieces in the soft iron rings for closing and releasing the valve openings. The guiding cage projects beyond the end of the soft iron ring so far that it slides in each displacement position of the valve piston on the closure pieces which are outwardly provided with guiding surfaces. The valve piston extends during its displacement movement through a circular opening in the central leg of the magnetic circuit, whereby a ring gap is produced between the central leg and the valve piston. In each abutment position of the actuating element the magnetic circuit of the permanent magnet which holds the actuating element with the valve member in its abutting position is closed through a soft iron piece, the associated end stop, the outer leg of the magnet core connected with it, the central leg of the magnet core, the ring gap remaining between the central leg and the valve piston, and the other soft iron piece. In order to maintain the magnetic voltage drop in the air gap low, narrow or tolerance limits must be maintained. This increased the manufacturing cost and affects the robustness of the magnetic valve.